Bubble column-type Fischer-Tropsch synthesis slurry bed reaction system

ABSTRACT

According to an exemplary embodiment, a bubble column-type slurry bed Fischer-Tropsch synthesis reaction process can be provided, in which synthesis gas supplied continuously from the bottom of a reactor contacts suspended catalyst particles to form liquid hydrocarbons, gaseous hydrocarbons and water. Additionally, a slurry of suspended liquid products and catalyst particles can move from the reactor to the lower portion of a separation vessel to separate the catalyst particles and gaseous products. Further, a process can be provided in which the liquid products formed are sent to the separation vessel a process in which liquid products can be derived. Additionally, a process can be provided in which a slurry in which catalyst particles are concentrated is derived from the bottom of the separation vessel and circulated to the bottom of the reactor, are driven by the driving force of synthesis gas without using an external drive power source.

TECHNICAL FIELD

The present invention relates to a bubble column-type slurry bedreaction system and apparatus that convert a synthesis gas composed ofhydrogen and carbon monoxide to liquid hydrocarbons product in thepresence of a suspended Fischer-Tropsch synthesis catalyst.

BACKGROUND ART

A Fischer-Tropsch synthesis reaction involves the reaction of asynthesis gas composed of hydrogen and carbon monoxide in the presenceof a solid catalyst to yield a mixture of paraffin and olefinhydrocarbons having a comparatively wide molecular weight distribution.Liquid hydrocarbons in particular are attracting attention as aclean-burning automobile fuel.

Fischer-Tropsch synthesis reactions are characterized as being extremelyexothermic. For example, the calorific value per kg-mol of carbonmonoxide in the following general formula (1) representing the synthesisof saturated hydrocarbons is about 40 Mcal.nCO+2nH₂→—(CH₂)_(n)—+nH₂O   (1)

Thus, one of the most important factors of processes involving thesynthesis of liquid hydrocarbons using the Fischer-Tropsch synthesismethod is the efficient removal of the heat of the reaction from thereactor.

Fixed bed heat exchange-type multi-tubular reactors, fluidized bedreactors and slurry bed reactors have been proposed as types ofFischer-Tropsch synthesis reactors that enable industrial synthesis ofliquid hydrocarbons from the synthesis gas while removing the heat ofthe reaction. Here, a slurry bed reaction system is a fluid reactionsystem in which three phases consisting of solid, liquid and gas phasesare present that introduce the synthesis gas into the suspension of aliquid medium and catalyst particles, and it is remarkably advantageousin comparison with other fixed bed systems in terms of the uniformity oftemperature profile in the reactor.

The use of a bubble column-type reactor has been advocated for slurrybed Fischer-Tropsch synthesis reaction systems, and catalyst particlesare maintained in a suspended state in the form of a slurry by kineticenergy of the synthesis gas that rises from the bottom of the reactor insuch a reactor(see, for example, Patent Documents 1 to 3).

One of the major subject of a bubble column-type slurry bed reactionsystem in which solid, liquid and gas phases are present is how theliquid hydrocarbon products can be efficiently separated and derivedfrom the three-phase slurry, and the use of filtration separation in themain reactor (see, for example, Patent Documents 3 and 4), filtrationseparation in a separate vessel connected to the main reactor with aconduit (see, for example, Patent Document 5), and hydrocycloneseparation (see, for example, Patent Document 6) have been advocated forthis purpose.

Patent Document 1: European Patent No EU 450,860

Patent Document 2: U.S. Pat. No. 6,348,510

Patent Document 3: U.S. Pat. No. 6,462,098

Patent Document 4: U.S. Pat. No. 5,844,006

Patent Document 5: U.S. Pat. No. 5,770,629

Patent Document 6: U.S. Pat. No. 6,121,333

DISCLOSURE OF THE INVENTION

However, in the case of filtration separation in the main reactor asadvocated in Patent Documents 3 and 4, since a filter is used for thefiltration means for separating the catalyst and liquid hydrocarbonproducts from the slurry, the occurrence of clogging of catalystparticles in the filter cannot be avoided. Therefore, a large number ofseparation and derivation pathways are provided and separation andderivation are carried out by mutually switching these pathways whileremoving catalyst particles that have become clogged by allowing liquidto flow back through clogged filter separation and derivation pathways.Consequently, the operating system involved in separation and derivationas well as the apparatus ends up being complex. In addition, since thecatalyst particles become powdered when clogging/removal is repeated, inaddition to causing deterioration of performance, there was also thepossibility of stable operation being difficult. Moreover, a combinationof coiled cooling tubes and downward tubes has been disclosed to ensuretemperature uniformity in slurry reactors suitable for efficientlyremoving the heat of the reaction, and these serve to evenly remove heatin the direction of the vertical axis of the reactor, however resultingin greater complexity of the apparatus configuration.

In addition, in the case of filtration separation in a separate vesselas described in Patent Document 5, a filter is also used as a filtrationmeans for separating the catalyst and liquid hydrocarbon products fromthe slurry. Consequently, there is still the occurrence of problemsaccompanying clogging of the filter by catalyst particles. In addition,although a slurry bed reactor is disclosed that. is suitable forefficiently removing the heat of the reaction, there is no disclosureregarding the cooling mechanism.

Moreover, in the case of hydrocyclone separation as described in PatentDocument 6, since external drive power source such as a pump and soforth is used during separation and derivation of the catalyst andliquid hydrocarbon products from the slurry, the catalyst particles aresubjected to a high load leading to deterioration of performance causedby attrition of the catalyst particles, and resulting in the problem ofdecreased production efficiency of FT synthesis oil. In addition, thereis also a problem of it being difficult to reduce costs due to thehigher running costs caused by the external drive power source. Inaddition, although Patent Document 6 discloses a slurry bed reactor thatis suitable for efficient removal of the heat of the reaction, there isno disclosure regarding the cooling mechanism.

As has been explained above, operating systems that separate and derivethe catalyst and liquid hydrocarbon products from the slurry composed ofsolid, liquid and gas phases in a bubble column-type slurry bed reactionsystem are complex, therefore creating the need for improvement by theuse of a simpler system. In addition, since it is extremely important tosynthesize liquid hydrocarbons by the Fischer-Tropsch synthesis reactionin the state in which a uniform temperature profile is maintained in thedirection of the vertical axis and radial direction, there is a need forthe synthesis reaction wherein a more uniform temperature profile ismaintained.

Therefore, in order to solve these problems, the object of the presentinvention is to provide a bubble column-type slurry bed reaction systemand apparatus capable of simplifying an operating system to be used tosynthesize liquid hydrocarbons by the Fischer-Tropsch synthesis reactionand separate and derive the catalyst and liquid hydrocarbon productsfrom the slurry composed of gas, liquid and solid phases, and reducingdeterioration caused by the attrition of catalyst particles.

In addition to the aforementioned object, another object of the presentinvention is to provide a bubble column-type slurry bed reaction systemand apparatus capable of synthesizing liquid hydrocarbons by theFischer-Tropsch synthesis reaction while maintaining a uniformtemperature profile in the vertical and radial directions.

In order to solve the aforementioned problems, the inventors of thepresent invention conducted extensive studies on a method for externallycirculating slurry between a bubble column-type slurry bed reactor(Fischer-Tropsch synthesis reactor) and a separation vessel, and amethod for cooling the bubble column-type slurry bed reactor, therebyleading to acquisition of the bubble column-type slurry bed reactionsystem of the present invention.

Namely, a first aspect of the present invention is: (1) a bubblecolumn-type slurry bed reaction system in the Fischer-Tropsch synthesisreaction system for producing liquid hydrocarbons by contacting thesynthesis gas composed of hydrogen and carbon monoxide with catalystparticles; wherein, (i) a bubble column-type slurry bed Fischer-Tropschsynthesis reaction process, in which synthesis gas supplied continuouslyfrom the bottom of a reactor and catalyst particles suspended in theliquid fractions are contacted to form liquid hydrocarbons, gaseoushydrocarbons and water, (ii) a process in which the slurry of suspendedliquid products formed in the Fischer-Tropsch synthesis reaction processand catalyst particles moves to the lower portion of a separation vesselthrough a downwardly inclined transfer pipe installed between thereactor and the lower portion of the separation vessel to separate thecatalyst particles and liquid products, (iii)a process in which thegaseous products formed in the Fischer-Tropsch synthesis reactionprocess is sent to the upper portion of the separation vessel through aconnecting pipe installed above the downwardly inclined transfer pipe,and derived from its apex, (iv) a process in which the liquid productsfrom which the majority of the catalyst particles from the separationvessel have been separated are derived, and (v) a process in which theslurry in which catalyst particles are concentrated is derived from thebottom of the separation vessel and circulated to the bottom of thereactor, is driven by the driving force (air lift) of synthesis gasintroduced from the bottom of the reactor and rises through the slurrybed reactor without using an external drive power source forcirculation, and the formed liquid hydrocarbon products, gaseoushydrocarbon products and water are separated and derived without usingan external drive power source for separation.

In addition, a second aspect of the present invention is a bubblecolumn-type slurry bed reaction system according to the first aspecthaving: (2) a process in which the temperature inside the reactor iscontrolled by a plurality of bayonet-type cooling tubes installedvertically from the upper portion of the bubble column-type slurry bedreactor and composed of cooling medium feed inner tubes and heatexchange outer tubes, and enabling the uniform removal of heat in theradial direction inside the reactor.

In the bubble column-type slurry bed reaction system of the presentinvention, the pressure of the reactor is 1 to 4 MPaG, and thesuperficial gas velocity is 0.05 to 0.2 m/second. In addition, 99% ormore of those catalyst particles introduced to the lower portion of theseparation vessel from said reactor having a particle diameter of 20 μmor more are circulated to said reactor. In the separation vessel of thepresent invention, which is connected to the bubble column-type slurrybed reactor by a downwardly inclined transfer pipe and has a slurryderivation pipe (slurry circulation pathway) that circulatescatalyst-concentrated slurry to said reactor, the liquid rise velocityinside said separation vessel is controlled to be 0.4 times or less thesedimentation velocity of 20 μm catalyst particles or less by acatalyst-concentrated slurry derivation control valve installed in theslurry derivation pipe (slurry circulation pathway) between saidseparation vessel and said reactor, a derivation control valve for theliquid reaction products, from which the majority of catalyst particleshave been separated, installed in a liquid reaction product derivationpipe extending from the separation vessel, and a differential pressurecontrol valve installed in a connecting pipe between the separationvessel and the upper gas phase space of said reactor.

In the reactor cooling process of the present invention that controlsthe temperature inside the reactor with a plurality of bayonet-typecooling tubes by feeding water (for example, boiler water) into theinner tubes, in addition to controlling the temperature inside thereactor to be at 210 to 280° C., steam at a temperature of 200 to 270°C. and pressure of 2 to 6 MPaG is obtained from the outer cooling tubeoutlet.

A third aspect of the present invention is (3) the Fischer-Tropschsynthesis reaction apparatus provided with a bubble column-type slurrybed Fischer-Tropsch synthesis reactor that forms liquid hydrocarbons,gaseous hydrocarbons and water by contacting synthesis gas continuouslysupplied from a gas distributor installed in the bottom of the reactorwith suspended catalyst particles; wherein, a circulation separationmechanism is provided that is driven by the driving force (air lift) ofthe synthesis gas rising through the slurry bed reactor introduced fromthe bottom of said reactor without using an external drive power sourcefor circulation, and separates and derives the formed liquid hydrocarbonproducts and gaseous hydrocarbon products without using an externaldrive power source for separation.

The said circulation separation mechanism has (i) the said reactor, (ii)a separation vessel that separates catalyst particles and liquidproducts by transferring a slurry, in which a liquid products formed insaid reactor and catalyst particles are suspended, through a downwardlyinclined transfer pipe connected between said reactor and the lowerportion of a separation vessel, (iii) a gaseous products derivationportion that transfers a gaseous products formed in the reactor to theupper portion of the separation vessel through a connecting pipeinstalled above the downwardly inclined transfer pipe, and derives thegaseous products from its apex, (iv) the liquid products derivationportion that derives the liquid products from said separation vessel,and (v) a circulation pathway unit that derives slurry in which catalystparticles have been concentrated from the bottom of said separationvessel and circulates it to the bottom of said reactor. In the saidcirculation separation mechanism, the reaction pressure inside thereactor can be controlled to be in the range of 1 to 4 MPaG and thesuperficial gas velocity can be controlled to be in the range of 0.05 to2 m/second. In addition, in said circulation separation mechanism, 99%or more of those particles introduced to the lower portion of theseparation vessel having a particle diameter of 20 μm or more can becirculated to said reactor. Moreover, in said circulation mechanism, theliquid rise velocity in the separation vessel can be controlled to be inthe range of 0.4 times or less the sedimentation velocity of catalystparticles having a particle diameter of 20 μm by a catalyst-concentratedslurry derivation volume control valve installed in the circulationpathway unit, a liquid reaction products derivation control valveinstalled in the liquid products derivation portion of the separationvessel, and a differential pressure control valve installed in aconnecting pipe between the separation vessel and the upper gas phasespace of the reactor.

In addition, a fourth aspect of the present invention is theFischer-Tropsch synthesis reaction apparatus according to the thirdaspect that is provided with a heat removal mechanism that controls thetemperature inside the reactor and enables uniform removal of heat inthe radial direction and vertical axis direction inside said reactor.

The heat removal mechanism has a plurality of cooling tubes comprised ofcooling medium feed inner tubes and heat exchange outer tubes installedvertically from the upper portion of the reactor, and by feeding waterinto the inner tube inlet in the upper portion of the reactor andallowing the water to pass through the inner tubes, flow through theouter tubes in the opposite direction and then flow out from the outertube outlet in the upper portion of the reactor, is able to control thereaction temperature inside the reactor to be from 210 to 280° C., whilealso being able to obtain steam at a temperature of 200 to 270° C. and apressure of 2 to 6 MPaG from the outer tube outlet. In addition, in theaforementioned heat removal mechanism, control of the temperature insidethe reactor can be controlled to be in a range of ±2° C. variation inthe reaction temperature inside the reactor.

In accordance with a bubble column-type slurry bed reaction system andapparatus of the present invention, since the system and apparatus aredriven by the driving force (air lift) of synthesis gas that risesthrough the inside of the slurry bed reactor after being introduced fromthe bottom of said reactor without using an external drive power sourcefor circulation, and is able to separate and derive liquid hydrocarbonproducts and gaseous hydrocarbon products formed without using anexternal drive power source for separation, there is less susceptibilityto the occurrence of attrition (physical destruction) of the catalystparticles, thereby making it possible to reduce deterioration ofperformance. In addition, since there is little susceptibility to theoccurrence of attrition, high-performance, inexpensive catalysts can bearbitrarily selected and used from available Fischer-Tropsch synthesiscatalysts without being restricted to only specific catalysts thatemphasize crush strength. In addition, since it is possible to monitorcirculation condition and because the internal structure is simple, theoccurrence of problems can be handled more quickly. Moreover,maintenance can be performed easily when a problem occurs. In addition,since there is no need to use a filter or external drive power source,and both the apparatus configuration and operating system can besimplified, running costs can be reduced.

In accordance with a bubble column-type slurry bed reaction system andapparatus of the present invention, since the system and apparatus havea process that allows heat of reaction to be uniformly removed in boththe vertical axis direction and radial direction of the reactor bycontrolling the temperature inside the reactor with a plurality ofcooling tubes composed of cooling medium feed inner tubes and heatexchange outer tubes, the heat can be uniformly removed from inside thereactor. As a result, the variation in the reaction temperature insidethe reactor can be controlled to be in a range of ±2° C. (refer to Table1 of the examples).

As a result, a bubble column-type slurry bed reaction apparatus can beprovided that has a simple operating system that synthesizes liquidhydrocarbons by the Fischer-Tropsch synthesis reaction, and separatesand derives catalysts and liquid hydrocarbon products from a slurrycomposed of gas, liquid and solid phases. Moreover, 99% or more of thosecatalyst particles introduced to the lower portion of a separationvessel from the upper portion of the bubble column-type slurry bedreactor can be circulated to the reactor by carrying out gravityseparation (sedimentation separation) utilizing the difference indensity between catalyst particles and liquid hydrocarbon products.Accordingly, liquid hydrocarbon products can be separated and derivedeasily by only sedimentation separation (gravity separation) from thecatalyst particles by using catalyst particles having a particlediameter of 20 μm or more for the total amount of catalyst particles. Inaddition, maintenance can be performed easily when a problem occurs.Moreover, this system and apparatus also offer the advantage of makingit easy to monitor circulation condition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration drawing of an example of a bubble column-typeFischer-Tropsch synthesis slurry bed reaction apparatus used in thepresent invention.

EXPLANATION ON SYMBOLS  1 FT synthesis reaction apparatus 11 Bubblecolumn-type slurry bed FT synthesis reactor 12 Separation vessel 21 Gasdistributor 22 Heat exchange tube 23 Horizontal connecting pipe 24Differential pressure control valve 25 Downwardly inclined transfer pipe26 Slurry circulation flow rate control valve (low differential pressureball valve) 27 Slurry circulation pathway 28 Liquid level control valve29 Flow meter 31 Boiler water inlet 32 Boiler water and steam outlet 33Gaseous components derivation outlet 34 Liquid hydrocarbon derivationpipe 41 Bubbles 42 Slurry 43 Liquid products 44 Catalystparticle-concentrated slurry 45 Aeration gas supply nozzle 51 Outer tube52 Inner tube 53 Tube seat 54 Tube seat 55 Inner tubes header 56 Outertubes header 57 Vertical connecting pipe 61 Gaseous components outflowcontrol valve

BEST MODE FOR CARRYING OUT THE INVENTION

The following provides a detailed explanation of a bubble column-typeslurry bed reaction system of the present invention based on FIG. 1.FIG. 1 is a configuration drawing of an example of a bubble column-typeFischer-Tropsch (FT) synthesis slurry bed reaction apparatus.

In an FT synthesis slurry bed reaction apparatus 1 shown in FIG. 1, asynthesis gas having a hydrogen/carbon monoxide molar ratio suitable forFT synthesis is continuously supplied from a gas distributor 21installed in the bottom of a bubble column-type slurry bed FT synthesisreactor 11, and is dispersed into the reactor 11 in the form of bubbles.

Here, the molar ratio of the hydrogen to carbon monoxide of thesynthesis gas suitable for FT synthesis is preferably 1.9 to 2.1. If themolar ratio of hydrogen to carbon monoxide is within this range, roughlythe entire amount can be supplied to the FT synthesis reaction of theaforementioned general formula (1), and the conversion efficiency (FTsynthesis oil production efficiency) for the target liquid hydrocarbonproducts (FT synthesis oil) can be enhanced. Furthermore, thecomposition of the synthesis gas may be such that, in addition tohydrogen and carbon monoxide gas, a hydrocarbon gas such as methane isalso contained as shown in Table 1 of the examples. Moreover, there arealso cases in which carbon dioxide is contained depending on the rawmaterials of the synthesis gas and production conditions, and this maybe removed as necessary according to the operating conditions and soforth.

In addition, there are no particular limitations on the flow rate of thesynthesis gas required to operate the apparatus, provided it allowsoperation by the driving force (air lift) of synthesis gas that risesthrough the slurry bed reactor introduced from the bottom of saidreactor without using an external drive power source for circulation.However, it is preferable to suitably determine the flow rate so as tosatisfy the superficial gas velocity conditions and so forth to bedescribed later, and to ensure a superior reaction efficiency throughcontact with catalyst particles during the residence time the synthesisgas rises through the reactor according to the size of the reactor, itsinternal shape and so on. In addition, although there are no particularlimitations on the size of the bubbles of the synthesis gas suppliedfrom the gas distributor provided it allows obtaining of the desiredsynthesis gas driving force (air lift) for the same reasons aspreviously described, it is preferably suitably determined so as tosatisfy the superficial gas velocity conditions and so forth describedlater.

In addition, there are no particular limitations on the shape of the gasdistributor 21, provided it allows synthesis gas to be supplieduniformly relative to the reactor cross-section, and known one in theprior art can be used as suitable.

Next, the dispersed synthesis gas causes the formation of reactionproducts containing liquid hydrocarbons by contacting catalyst particlessuspended in a medium while rising through the reactor 11.

Inside the reactor 11, bubbles 41 composed of synthesis gas, gaseousreaction products and unreacted gas and a slurry 42 composed of catalystand liquid reaction products flow in a suspended state. The operatingconditions of the reactor consist of a pressure of 1 to 4 MPaG,temperature of 210 to 280° C. and superficial gas velocity of about 0.05to 0.20 m/second.

Slurry 42 is favorably mixed in the vertical axis and radial directionsof the reactor accompanying the agitating more of the bubbles 41 underthe aforementioned superficial gas velocity conditions. As a result ofemploying these operating conditions, a maximum CO conversion of 90% canbe achieved in general formula (1) representing the previously describedFT synthesis reaction.

Here, the liquid hydrocarbon products (FT synthesis oil) are preferablyused for the initially charged solvent. However, there are no particularlimitations on the initially. charged solvent, provided it does not havean effect on the application of the liquid hydrocarbon products or FTsynthesis reaction after being derived together with the liquidhydrocarbon products, and should be able to form a slurry by suspendingcatalyst particles. This initially charged solvent is replaced withliquid hydrocarbon products (FT synthesis oil) subsequently formedduring the continuous operation.

The aforementioned catalyst is in the form of particles, and anyFischer-Tropsch synthesis catalyst known in the prior art can besuitably used, provided it allows the formation of a slurry by beingsuspended in a medium, the details of which are described later.

In the case that the reaction pressure of the aforementioned reactor isless than 1 MPaG, there is the possibility of catalyst activity beinginadequate, while in the case that it exceeds 4 MPaG, there is thepossibility of increasing the cost of the reactor. In the case that thereaction temperature is lower than 210° C., there is the possibility ofcatalyst activity being inadequate, while in the case that it exceeds280° C., there are many cases in which the conditions are not suitablefor an FT synthesis reaction, although dependent on the catalyst used.In the case that the superficial gas velocity is less than 0.05m/second, it is becomes difficult for the agitating move of the bubblesto occur, thereby resulting in the possibility of inadequate mixing ofthe slurry. In the case that the superficial gas velocity exceeds 0.20m/second, the volume of gas inside the reactor becomes excessivelylarge, resulting in the possibility of increasing the cost of thereactor. In addition, there are no particular limitations on theconcentration of the catalyst (solid component) in the slurry under theaforementioned operating conditions, provided it satisfies theaforementioned superficial gas velocity, and is normally within therange of 10 to 40% by weight and preferably 20 to 30% by weight. In thecase that the catalyst concentration in the slurry is less than 10% byweight, there is the possibility of the reactor becoming too largecompared to the production needed. In the case the catalystconcentration exceeds 40% by weight, it becomes difficult for thecatalyst to be dispersed (mixed) in the slurry, thereby resulting in therisk of the FT synthesis reaction being unable to proceed adequately.The aforementioned reactor operating conditions can be controlled bycooling tubes and various control valves provided in the reactor as willbe described later, or by the flow rate of the synthesis gas andcatalyst concentration.

Next, slurry 42, in which liquid hydrocarbons formed by the FT synthesisreaction and catalyst particles are suspended, is supplied to the lowerportion of a separation vessel (12) through a downwardly inclinedtransfer pipe 25 installed in the upper portion of the reactor. Theangle of inclination of the downwardly inclined transfer pipe 25 ispreferably 30 to 45 degrees, and the slurry transfer velocity ispreferably about 0.4 to 1.6 m/second.

Furthermore, in the case that the slurry transfer velocity is less than0.4 m/second, there is the possibility of a portion of the catalystparticles accumulating in the bottom of the pipe as a result of unstableslurry circulation, which in turn has the possibility of causinginadequate mixing of slurry inside the reactor.

Although FIG. 1 shows an embodiment in which a single separation vessel12 is provided, the present invention is not limited to this, but rathera plurality of separation vessels may also be provided. However, onlyone separation vessel should be provided from the viewpoint ofsimplifying the apparatus and operating system. Similarly, although theembodiment shown in FIG. 1 depicts a single downwardly inclined transferpipe between the reactor and separation vessel, the present invention isnot limited to this, but rather a plurality of such pipe may also beprovided. However, a single pipe is appropriate from the viewpoint ofsimplifying the apparatus and operating system.

Next, slurry supplied to the lower portion of the separation vessel 12is separated by gravity in the separation vessel 12 into a liquidproducts 43, from which the majority or all of the catalyst particleshave been separated, and a catalyst particle-concentrated slurry 44 dueto the difference in density between the catalyst particles and liquidproducts. Liquid products 43 is sent out to be used in a downstreamprocess such as liquid hydrocarbon separation and purification equipmentfrom a derivation pipe 34 (liquid products derivation portion) installedat an intermediate portion of the separation vessel 12 (below the rangeof the fluctuation of the level of liquid during stable operation of theapparatus) while controlling the liquid level in the separation vessel12 with a liquid level control valve 28. Gravity-separated catalystparticle-concentrated slurry 44 is circulated to the bottom of thereactor 11 through a slurry circulation pathway 27 and a flow ratecontrol valve 26, to be reused as catalyst for the FT synthesisreaction. The slurry circulation velocity is preferably about 0.4 to 1.6m/second.

The gas phase space in the upper portion of the reactor 11 and the gasphase space in the upper portion of the separation vessel 12 areconnected with a horizontal connecting pipe 23, being connected to thedownwardly inclined transfer pipe 25 with a vertical connecting pipe 57,and the pressure difference between the gas phase space in the upperportion of the reactor 11 and the gas phase space in the upper portionof the separation vessel 12 is controlled with a differential pressurecontrol valve 24. The gaseous products separated in the reactor 11,separation vessel 12 and downwardly inclined transport pipe 25 and thegaseous components of the unreacted synthesis gas are sent outside thesystem from a derivation outlet 33 installed in the apex of theseparation vessel 12, and their flow rate is controlled by the gaseouscomponents outflow control valve 61. Furthermore, the aforementionedconnecting pipes should enable the gaseous components formed in thereactor to be transferred to the separation vessel by passing throughpipes connected between the gas phase portions of the reactor andseparation vessel. Thus, in addition to the pipe connected horizontallybetween the reactor 11 and the separation vessel 12 (horizontalconnecting pipe 23) shown in FIG. 1, these connecting pipes may also beconnected at an angle, and there are no particular limitations thereon.

The method used by the bubble column-type slurry bed reaction system ofthe present invention to separate catalyst particles and liquidhydrocarbon products is such that, in the gravity separation within theseparation vessel 12, the velocity at which the liquid products 43, fromwhich the majority or all of the catalyst particles have been separated,passes through the separation vessel is controlled to be 0.4 times orless the terminal sedimentation velocity of catalyst particles having aparticle diameter of 20 μm, and as a result, realizes a separationefficiency of 99% or more for catalyst particles having a particlediameter of 20 μm or more. As a result, since the catalyst particles arenot subjected to filtration or drive power, there is littlesusceptibility to catalyst attrition (physical destruction), which inturn leads to catalyst stability (long service life). Consequently,deterioration of performance can be inhibited and costs can be reduced.

On the basis of the above, the use of catalyst particles having aparticle diameter of 20 μm or more as specified by sieving and so forthcan be said to be preferable in the present invention. Namely, in casesin which the catalyst particles contain a large amount of particleshaving a particle size of less than 20 μm, even if the velocity at whichthe liquid products rises through the separation vessel is controlled aspreviously described, it is difficult to separate catalyst particleshaving a smaller particle diameter using gravity. As a result of usingsufficiently large particles, liquid products can be derived in whichthe catalyst particles have been separated by gravity (sedimentationseparation). However, since a minute amount of catalyst particles canbecome mixed into the derived liquid of liquid products due to attritionof the catalyst and so forth during continuous operation, an auxiliaryfilter may be provided at the liquid products derivation outlet.

The velocity at which the liquid products 43 rises through theseparation vessel is controlled by the operating control valves 24, 26and 28, and substantially controlled by operating low differentialpressure ball valves in the form of the slurry circulation flow ratecontrol valve 26 and the liquid products derivation control valve 28,and the rise velocity of the oil formed in the separation vessel 12(liquid hydrocarbon products) is maintained at 0.4 times or less theterminal sedimentation velocity of catalyst particles having a particlediameter of 20. In addition, the rise velocity of oil formed in theseparation vessel 12 (liquid hydrocarbon products) is determined fromthe flow rate of the formed oil derived from the derivation pipe 34.Here, in the case that the rise velocity of oil formed inside theseparation vessel 12 (liquid hydrocarbon products) is greater than 0.4times the terminal sedimentation velocity of catalyst particles having aparticle diameter of 20 μm, it becomes difficult to realize separationefficiency of 99% or more for catalyst particles having a particlediameter of 20 μm or more. Namely, there is the risk of it becomingdifficult to separate catalyst particles and liquid hydrocarbon productsusing gravity separation instead of filtration separation in the mannerof the prior art.

As has been described above, the present invention is characterized by aslurry, in which catalyst particles and liquid products are suspended,naturally circulating between a reactor 11 and a separation vessel 12without using a pump or other external drive power source due to adriving force (air lift) generated when bubbles of the synthesis gassupplied from the bottom of reactor 11 rise through the slurry, and thedifference in density between fluids respectively present in reactor 11and separation vessel 12. The circulation velocity of the slurry iscontrolled to be about 0.4 to 1.6 m/second by a low differentialpressure ball valve 26 and a flow meter 29 installed in the verticalportion of the slurry circulation pathway 27. In addition, since theoperation of circulating the slurry is carried out by naturalcirculation, a bubble column-type slurry bed reaction system can beprovided that achieves stable operation for a long period of timewithout causing wear or destruction of catalyst particles. Moreover,since the bubble column-type slurry bed reaction system of the presentinvention separates and derives liquid hydrocarbon products fromcatalyst particles without using an external drive power source, abubble column-type slurry bed reaction system can be provided that haslow running costs.

The following provides a more detailed description of the flow ratecontrol method used in the bubble column-type slurry bed reaction systemof the present invention.

As was previously described, the slurry circulation velocity iscontrolled to be about 0.4 to 1.6 m/second by a slurry circulation flowrate control valve 26 installed in the bottom of the circulation pathway27.

An aeration gas supply nozzle 45 is preferably installed in thecirculation pathway 27 to further smoothen the circulation of slurry.Nitrogen, hydrogen or synthesis gas can be used for the aeration gas aslong as it does not deactivate catalyst activity. Supply nozzles 45 arepreferably installed at a plurality of locations in the circulationpathway 27 as necessary. This aeration gas is constantly orintermittently injected to increase the slurry circulation drivingforce, and is particularly important at the start of slurry circulationwhen there is considerable inertial resistance.

A differential pressure control valve 24 that controls the pressuredifference between the two columns is installed in the horizontalconnecting pipe 23 between the reactor 11 and the separation vessel 12.A low differential pressure ball valve is used for the differentialpressure control valve 24. The difference between the respective liquidlevels in the reactor 11 and separation vessel 12 is suitably maintainedby the differential pressure control valve 24 to realize stable naturalcirculation of slurry. In addition, the horizontal connecting pipe 23and downwardly inclined transfer pipe 25 are connected by a verticalconnecting pipe 57. This vertical connecting pipe 57 prevents overflowof slurry from the horizontal connecting pipe 23 into the separationvessel 12 due to excessive rising of the level of the slurry in thereactor 11, and has the effect of separating bubbles that have enteredthe downwardly inclined transfer pipe 25, thereby promoting the gravityseparation of catalyst particles, liquid products and gaseous componentsin the separation vessel 12.

The FT synthesis catalyst used in the bubble column-type slurry bedreaction system of the present invention is in the form of particles andenables the formation of a slurry by being suspending in a medium oil.Cobalt or ruthenium catalysts, for example, are preferably used. Theparticle diameter of the FT synthesis catalyst is 20 μm or more, and themean particle diameter is preferably within the range of 50 to 150 μm.

Heat exchange tubes 22 are inserted into the reactor 11 to remove thelarge amount of heat generated accompanying the FT synthesis reaction inthe bubble column-type FT synthesis slurry bed reaction system of thepresent invention. Although there are no particular limitations on thecooling method that these heat exchange tubes use, bayonet-type coolingtubes are used in FIG. 1 since they are superior for controllingtemperature distribution temperature profile. In the embodiment shown inFIG. 1, a plurality of bayonet-type cooling tubes composed of coolingmedium feed inner tubes and heat exchange outer tubes are installedvertically from the upper portion of the reactor to control thetemperature inside the reactor and enable uniform removal of heat in theradial and vertical axis directions within said reactor. The structureof these tubes is composed of an outer tube 51 and an inner tube 52,they are disposed at a suitable pitch (and preferably a triangularpitch) on tube seats 53 and 54, respectively, and they have a boilerwater inlet 31 and a boiler water and steam outlet 32. Inside the tubes,cooling water from the boiler water inlet is supplied to the inner tube52 of each tube through the inner tube header 55, steam is generatedfrom a portion of the boiler water by the heat generated by the FTsynthesis reaction when it passes through the outer tube 51, the mixedphase fluid of steam and water is sent out from the outlet 32 afterpassing through the outer tube header 56, and the generated steam isrecovered in the form of plant steam. The operating conditions consistof a pressure of 2.0 to 6.0 MPaG and a temperature of 200 to 270(C, andthe ratio of steam generated from the boiler water by removing the heatgenerated by the FT synthesis reaction is preferably 5 to 10% by weight.The bayonet-type cooling tubes are able to uniformly control thetemperature distribution temperature profile in the reactor byefficiently removing the large amount of heat generated accompanying theFT synthesis reaction (roughly 40 Mcal/kgmol-CO), thereby realizingstable operation. In addition, since the structure of the system ischaracterized by the presence of expansion of freedom at the bottom ofthe tubes, it is not necessary to take into consideration the problem ofthermal expansion of the cooling tubes during operation. Vibration ofthe cooling tubes can be prevented to enable stable operation by causingthe flow pattern in the outer tubes in the form of dual phase flow in avertical tube to approach a annual/atomized flow as a result ofoperating while making the ratio of steam generated from the boilerwater be 5 to 10% by weight.

Here, the operating conditions of the cooling apparatus are preferablyset so as to obtain steam at a pressure of 2.0 to 6.0 MPaG and atemperature of 200 to 270 (C from the cooling tube outer tube outlet byfeeding water (for example, boiler water) into the cooling tube innertube. The temperature inside the reactor is also preferably controlledto be 210 to 280(C. In the case of using the aforementioned bayonet-typecooling tubes in particular, the resulting control of the temperatureinside the reactor can be carried out stably at a range of variation inthe reaction temperature inside the reactor of (5 (C and preferably (2(C (refer to Table 1 in the examples described later).

Furthermore, although it is difficult to universally define thepositional relationship between the reactor and separation vessel usedin the bubble column-type slurry bed reaction system of the presentinvention due to differences in the size of the two vessels and soforth, a positional relationship may be taken that allows circulation ofslurry, and there are no particular limitations on this relationshipprovided the gas phase portions of the reactor 11 and the separationvessel 12 are connected with a pipe in the manner of the connecting pipe23 as shown in FIG. 1, and the effects and action in the form of theslurry moving to the lower portion of the separation vessel 12 throughthe transfer pipe 25 of the invention of the present application are notimpaired.

The following provides an explanation of examples of the presentinvention.

EXAMPLE 1

The reaction apparatus shown in FIG. 1 was used for the reactionapparatus.

Liquid hydrocarbon was produced by an FT synthesis reaction by supplyingsynthesis gas at a feed rate of 250 Nm³hour (100% load) and controllingthe reaction pressure to be 2200 kPaG and the reaction temperature to be240° C. (±2° C.). The results are shown in Table 1. In addition tocontrolling the reaction temperature inside the reactor to be in theaforementioned temperature range, boiler water was fed into the innertubes of a plurality of bayonet-type cooling tubes, and controlled so asto obtain steam having a temperature of 231° C. and a pressure of 2735kPaG from the cooling tube outer tube outlet. In addition, the COconversion during this FT synthesis reaction was 62% under theseoperating conditions.

The temperature profile inside the reactor demonstrated a uniformtemperature profile in which the temperature difference in the directionof the vertical axis of the reactor was 2° C. or less under theconditions of a superficial gas velocity of 0.15 m/second, and heatgenerated by the FT synthesis reaction was confirmed to be efficientlyremoved by the bayonet-type cooling tubes. Under the conditions ofExample 1, FT synthesis oil (liquid hydrocarbon) was produced at 5.0barrels/day.

EXAMPLE 2

A liquid hydrocarbon was produced by an FT synthesis reaction bysupplying a synthesis gas at a feed rate of 100 Nm³hour (40% load) andcontrolling the reaction pressure to be 2200 kPaG and the reactiontemperature to be 230° C. using the same reaction apparatus as inExample 1. The results are shown in Table 1. In addition to controllingthe reaction temperature inside the reactor to be in the aforementionedtemperature range, boiler water was fed into the inner tubes of aplurality of bayonet-type cooling tubes, and controlled so as to obtainsteam having a temperature of 226° C. and a pressure of 2450 kPaG fromthe cooling tube outer tube outlet. In addition, the CO conversionduring this FT synthesis reaction was 89% under these operatingconditions.

The temperature profile inside the reactor demonstrated a uniformtemperature profile in which the temperature difference in the directionof the vertical axis of the reactor was 1° C. or less under theconditions of a superficial gas velocity of 0.06 m/second, and heatgenerated by the FT synthesis reaction was confirmed to be efficientlyremoved by the bayonet-type cooling tubes. Under the conditions ofExample 2, FT synthesis oil (liquid hydrocarbon) was produced at 2.6barrels/day.

TABLE 1 Example 1 2 Synthesis gas Composition (mol %) H2 60.34 61.53 CO29.41 30.09 CH4 8.70 5.79 CO2 0.00 0.00 Flow rate (Nm³/hr) 250 100Reactor Pressure (kPaG) 2200 2200 Temperature (° C.) Upper portion (EL =11950 mm) 238 238 230 230 Mid-upper portion (EL = 8100 mm) 240 238 231230 Middle portion (EL = 5400 mm) 240 240 230 230 Mid-lower portion (EL= 2700 mm) 240 240 229 229 Lower portion (EL = 0 mm) 240 229 Superficialgas velocity (m/sec) 0.15 0.06 Separation Vessel Liquid level (%) 50 72Liquid level rise velocity (m/sec) 3.7 × 10⁻⁵ 1.9 × 10⁻⁵ 20 μm particleterminal 1.0 × 10⁻³ 1.0 × 10⁻³ sedimentation velocity Reactor/separationvessel Superficial gas velocity (kPa) 4.8 1.3 Slurry circulation flow0.75 0.78 velocity (m/sec) FT synthesis oil production (barrels/day) 5.02.6

Furthermore, the temperatures of the reactor shown in Table 1 indicatethe values of a temperature sensors provided at each location inside thereactor. However, the two values shown in the columns for the upperportion, mid-upper portion, middle portion and mid-lower portion of thereactor indicate the values of a plurality (two) of temperature sensorsprovided within the same plane of the reactor. The locations where thetemperature sensors were installed in the direction of the vertical axis(upper portion: A, mid-upper portion: B, middle portion: C, mid-lowerportion: D, lower portion: E (EL=0 mm)) are shown in FIG. 1. Inaddition, seven cooling tubes were disposed at a triangular pitch.

INDUSTRIAL APPLICABILITY

The present invention can be applied to a bubble column-type slurry bedreaction system and apparatus capable of synthesizing liquidhydrocarbons by the Fischer-Tropsch synthesis reaction.

1. A bubble column-type slurry bed reaction system in a Fischer-Tropschsynthesis reaction system for producing liquid hydrocarbon products bycontacting a synthesis gas composed of hydrogen and carbon monoxide withcatalyst particles, the slurry bed reaction system comprising: a gasdistributor arrangement configured to supply the synthesis gascontinuously from a bottom of a reactor so that the synthesis gascontacts the catalyst particles that are suspended to form the liquidhydrocarbon products, gaseous hydrocarbon products, and water in aFischer-Tropsch synthesis reaction procedure; a downwardly inclinedtransfer pipe arrangement configured to transfer the suspended liquidhydrocarbons formed in the Fischer-Tropsch synthesis reaction procedureand catalyst particles from the reactor to a lower portion of aseparation vessel to separate the catalyst particles and the liquidhydrocarbon products; and a connecting pipe arrangement which isinstalled above the downwardly inclined transfer pipe arrangement andconfigured to supply the gaseous hydrocarbon products formed in theFischer-Tropsch synthesis reaction procedure to an upper portion of theseparation vessel, wherein: the slurry bed reaction system is configuredsuch that the liquid hydrocarbon products are derived from theseparation vessel, a slurry in which the catalyst particles areconcentrated is derived from a bottom of the separation vessel andcirculated to the bottom of the reactor, and is driven by a drivingforce of the synthesis gas introduced from the bottom of the reactor andwhich rises through the reactor without using an external drive powersource for a circulation, and the formed liquid hydrocarbon products,gaseous hydrocarbon products and water are separated and derived withoutusing the external drive power source for the separation, and theseparation vessel includes a slurry circulation pathway that circulatesa catalyst particle-concentrated slurry to the reactor and a liquid risevelocity inside the separation vessel is controlled to be 0.4 times orless of a sedimentation velocity of catalyst particles having a particlediameter of 20 μm by a catalyst-concentrated slurry derivation ratecontrol valve installed in the slurry circulation pathway between theseparation vessel and the reactor, a derivation rate control valve forthe liquid hydrocarbon products derived from the separation vessel, anda differential pressure control valve in an upper gas phase spacebetween the separation vessel and the reactor.
 2. The bubble column-typeslurry bed reaction system according to claim 1, wherein a temperatureinside the reactor is controlled by a plurality of cooling tubesinstalled vertically from an upper portion of the reactor, and composedof cooling medium feed inner tubes and heat exchange outer tubes, andfacilitating a uniform removal of heat in a radial direction and avertical axial direction inside the reactor.
 3. The bubble column-typeslurry bed reaction system according to claim 1 or 2, wherein the slurrybed reaction system is configured such that a pressure of the reactor is1 to 4 MPaG, and a superficial gas velocity inside the reactor is 0.05to 0.2 m/second during the Fischer-Tropsch synthesis reaction procedure.4. The bubble column-type slurry bed reaction system according to any ofclaims 1 or 2, wherein the slurry bed reaction system is configured suchthat 99% or more of those catalyst particles introduced to the lowerportion of the separation vessel from the reactor having a particlediameter of 20 μm or more are circulated to the reactor.
 5. The bubblecolumn-type slurry bed reaction system according to claim 2, wherein theslurry bed reaction system is configured such that the temperature iscontrolled inside the reactor by feeding water into the cooling tubeinner tubes to be at 210 to 280° C., and wherein the slurry bed reactionsystem is further configured such that a steam is maintained at atemperature of 200 to 270° C. and a pressure of 2 to 6 MPaG is obtainedfrom a cooling tube outer tube outlet.
 6. A Fischer-Tropsch synthesisreaction apparatus, comprising: a bubble column-type slurry bedFischer-Tropsch synthesis reactor that forms liquid hydrocarbonproducts, gaseous hydrocarbon products and water by contacting synthesisgas continuously supplied from a gas distributor installed in a bottomof the reactor with suspended catalyst particles; and a circulationseparation mechanism that is (a) driven by a driving force of thesynthesis gas rising through the slurry bed reactor introduced from thebottom of the reactor without using an external drive power source for acirculation, and (b) separates and derives the formed liquid hydrocarbonproducts and gaseous hydrocarbon products without using the externaldrive power source for the separation, wherein: the circulationseparation mechanism includes: (a) the reactor, (b) a separation vesselthat separates catalyst particles and liquid hydrocarbon products bytransferring a slurry, in which the liquid hydrocarbon products formedin the reactor and the catalyst particles are suspended, through adownwardly inclined transfer pipe arrangement connected between thereactor and a lower portion of the separation vessel, (c) a gaseoushydrocarbon products derivation portion that transfers the gaseoushydrocarbon products formed in the reactor to an upper portion of theseparation vessel through a connecting pipe installed above thedownwardly inclined transfer pipe, and derives the gaseous products fromits apex, (d) a liquid hydrocarbon products derivation portion thatderives the liquid hydrocarbon products from the separation vessel, and(e) a circulation pathway that derives the slurry in which the catalystparticles have been concentrated from the bottom of the separationvessel, and circulates the circulation pathway to the bottom of thereactor, and wherein, in the separation circulation mechanism, a liquidrise velocity inside the separation vessel is controlled to be 0.4 timesor less of a sedimentation velocity of the catalyst particles having aparticle diameter of 20 μm by a catalyst-concentrated slurry derivationrate control valve installed in the slurry circulation pathway betweenthe separation vessel and the reactor, a derivation rate control valvefor the liquid hydrocarbon products derived from the separation vessel,and a differential pressure control valve in an upper gas phase spacebetween the separation vessel and the reactor.
 7. The Fischer-Tropschsynthesis reaction apparatus according to claim 6, wherein theFischer-Tropsch synthesis reaction apparatus is configured such that areaction pressure inside the reactor is controlled to be in the range of1 to 4 MPaG and a superficial gas velocity is controlled to be in therange of 0.05 to 0.2 m/second.
 8. The Fischer-Tropsch synthesis reactionapparatus according to claim 7, wherein the Fischer-Tropsch synthesisreaction apparatus is configured such that in the circulation separationmechanism, 99% or more of those particles introduced to the lowerportion of the separation vessel having a particle diameter of 20 μm ormore are circulated to the reactor.
 9. The Fischer-Tropsch synthesisreaction apparatus according to claim 6 or 7, further comprising a heatremoval mechanism that controls a temperature inside the reactor andenables uniform removal of heat in a radial direction and a verticalaxis direction inside the reactor.
 10. The Fischer-Tropsch synthesisreaction apparatus according to claim 9, wherein the heat removalmechanism has a plurality of cooling tubes comprised of cooling mediumfeed inner tubes and heat exchange outer tubes installed vertically froman upper portion of the reactor, and by feeding water into an inner tubeinlet in the upper portion of the reactor, and facilitating the water topass through the inner tubes, flow through the outer tubes in anopposite direction and then flow out from an outer tube outlet in theupper portion of the reactor, controls a reaction temperature inside thereactor to be at 210 to 280° C., while also obtaining steam at atemperature of 200 to 270° C. and a pressure of 2 to 6 MPaG from theouter tube outlet.
 11. The Fischer-Tropsch synthesis reaction apparatusaccording to claim 9, wherein the heat removal mechanism is configuredto control the temperature inside the reactor to be in a range of ±2° C.variation in the reaction temperature inside the reactor.